Lev Ageyeva, now six, was 14 months old when Elton and long-term partner David Furnish found him in an orphanage near Donetsk in September 2009 and announced their wish to adopt the boy. At the time, the singer said that Lev 'has stolen my heart'.
However, the couple's attempt was thwarted by Ukrainian laws which prevent gay men from adopting. Elton's age - he was 62 at the time - was also cited as an obstacle to proceedings.
Elton and David went on to have two sons in the UK via surrogate - Zachary, born Christmas Day 2010, and Elijah, born January 2013 - while Lev was taken in by his grandmother, Yulia.
Even though their attempt to adopt Lev ended in disappointment, Elton and David vowed that they would continue to support the boy financially and look out for him as he grew up.
According to a close friend of the couple, they have now done just that.
Story continues after the video...
Lev and his family have been living in the south-eastern city of Mariupol. But with Russian-backed separatists threatening to launch an attack on the city, and citizens frantically digging trenches to repel an invasion, Lev and his family were desperate to escape.
Step forward, Sir Elton...
The Daily Mail reports that Olena Pinchuk, Ukraine's most influential businesswomen, has told news outlets that Elton and David were part of a dramatic rescue mission to spirit Lev and his relatives away from advancing pro-Russian troops.
Pinchuk, daughter of former Ukrainian president Leonid Kuchma, is well known to Elton through her high-profile work with the ANTIAIDS charity she founded in 2003 to raise Aids awareness in Ukraine.
The foundation arranged for Lev and his family to be evacuated from the city and brought nearly 500 miles to the relative safety of Ukrainian capital Kiev, in an operation believed to have been backed by Elton and David.
Yulia Ageyeva, 61, grandmother of Lev and seven-year-old brother Artyom, did not know if the rescue was Elton's response to her plea in May this year for the singer to help the family flee Mariupol, but said: "I thank God for whoever helped us."
The singer's representative has yet to comment on the story.